Last week, I discussed the most vulnerable senator seeking re-election. It was a tough call, but clearly came down to two Southern Democrats. This week, the question is who is the House’s most vulnerable incumbent, and the answer is much, much easier.

It’s California Republican Gary G. Miller.

Miller is an eight-term Republican from San Bernardino County, and he isn’t vulnerable because of something he did. Until last year, the real estate developer and former California state assemblyman represented a reliably Republican, Orange County-based district that also included parts of Los Angeles County and San Bernardino County.

But redistricting after the 2010 census changed all that, and instead of opting for a member-vs.-member primary against fellow Republican Rep. Ed Royce, Miller decided to run in the newly created 31st District, territory he had not previously represented.

Democrats pretty much took this seat for granted after it was created, figuring they’d recruit a strong nominee and have little trouble winning in a presidential year. The district has a majority of minority voters (the district is 44 percent Hispanic and more than 11 percent black), and Barack Obama carried it with 57 percent of the vote in 2008 and 2012.

But Redlands Mayor Pete Aguilar (22.6 percent) got nosed out in the open primary by two Republicans — Miller (26.7 percent) and state Sen. Bob Dutton (24.8 percent) — so Democrats didn’t have a candidate in November. Three lower-tier Democrats combined to get more than a quarter of the open primary vote, thereby allowing the two Republicans to move on to November, when Miller won with 55 percent.

The congressman received considerable help from the National Association of Realtors, which spent heavily on mail and cable TV ads.

This time, national Democrats will keep closer tabs on the district, and they have plenty of reasons to believe that they’ll have a candidate on the November ballot. Aguilar is running again, and his early start proves that he has learned his lesson. Former Democratic Rep. Joe Baca recently made clear he is running in the district as well.

Even Republicans admit that Miller will have a tough time holding onto his seat if he faces a strong Democratic opponent in the next general election. The numbers are simply against him.

After Miller, the next most vulnerable incumbent is Tennessee Republican Rep. Scott DesJarlais, who has suffered from a series of revelations about his personal and professional life. GOP state Sen. Jim Tracy already has $400,000 in the bank, and only the possibility of a large primary field that might divide the anti-DesJarlais vote would seem to give the congressman much of a chance of winning renomination to another term.

After Miller and DesJarlais, there are a handful of obvious candidates for the next most vulnerable House incumbent.

Barber beat Republican Martha McSally by fewer than 2,500 votes, even though she started late and was generally underestimated by party insiders, who talked about her appeal but emphasized the challenges facing her bid.

McSally is likely to run again, and her personal appeal is considerable. Combine that with a stronger campaign and a midterm electorate, and Barber is in great danger in what should be a Democratic-leaning district.

Coffman defeated Joe Miklosi by 7,001 votes, or about 2 points (47.8 percent to 45.8 percent). Miklosi wasn’t initially regarded by Democratic insiders as the party’s ideal challenger, but “outside” groups ended up spending almost $3.9 million for him, according to the Campaign Finance Institute.

This cycle, Democrats got a top recruit in former Colorado Speaker Andrew Romanoff, who chose to primary appointed Democratic Sen. Michael Bennet in 2010, rather than run for the House against Coffman. Miklosi didn’t live in the district when he ran last cycle, while Romanoff moved into the district earlier this year.

Two incumbents who were almost given up for dead (politically, that is) last cycle but survived — Democratic Reps. Jim Matheson of Utah and Mike McIntyre of North Carolina — are likely to face stiff challenges again. Either or both could move to the top of the vulnerability list next year.

Democratic partisans may pooh-pooh the danger to both incumbents in 2014, noting that we have heard reports of their problems before and saying that if the two Democratic congressmen won with an unpopular (in their districts) president on the ballot, they certainly can win again against the same opponents in 2014.

Republicans can counter that unsuccessful 2012 Utah Republican nominee Mia Love didn’t run nearly as good a race as GOP strategists had hoped, and she’ll likely have a better campaign — and be a better candidate — in a rerun.

The same, of course, could hold for the unsuccessful GOP nominee against McIntyre last year, David Rouzer. Rouzer, then a member of the state Senate, lost to McIntyre by a mere 654 votes in 2012.

While the landscape of the Senate already looks pretty clear, the outlook for individual House races is likely to change a lot this year as candidates enter (and possibly exit) contests. So a race that already looks very competitive now could fall off most lists a year from now, and a district that starts off as a yawner now could be a hot contest 18 months from today.

Stuart Rothenberg (@stupolitics) is editor of the Rothenberg Political Report (rothenbergpoliticalreport.com). Read more at his blog, Rothenblog (blogs.rollcall.com/rothenblog).

Corrects the year that Andrew Romanoff ran against Sen. Michael Bennet. It was 2010.